This invention relates to the field of impact free magnetographic printers, and more particularly to printing processes used in this type of printer.
Magnetographic printers comprise a magnetic recording element that may be in various forms such as for example a drum, a tape or a disk. The magnetic recording element is composed of a substrate coated with a layer of magnetic material. Information is recorded on this element by means of at least one recording device called a module. The module comprises at least one elementary magnetic recording head close to which the recording element is moving. The elementary recording head is usually composed of an electromagnet.
Each of the elementary heads generates a magnetic field each time that it is excited by an electric current with a determined intensity, which has the effect of creating small magnetized areas on the surface of the recording element that advances in front of these elementary heads. These concentrated magnetized areas are usually called magnetized recorded dots. The portion of the surface of the element that passes in front of each head is usually called information recording tracks.
The magnetized recorded dots located on one recording track and preceded in the direction in which the recording element advances by at least one recorded dot that was not magnetized belong to a set of magnetized recorded dots called a leading edge.
The combination of recorded dots forms an image. Particles of magnetic ink are then attracted by recorded dots magnetized on the recording element. Paper to be printed is pressed in contact with the recording element. Particles of magnetic ink are transferred onto the paper and fixed on it; the image formed by recorded dots on the drum is transferred to paper using particles of magnetic ink.
It is found that as the speed of the recording element increases, the amount of ink applied for the magnetized recorded dots belonging to the leading edges reduces. The work done by the magnetic development force is not sufficient to deposit ink particles over the entire area of each magnetized recorded dots on the leading edge.
One purpose of this invention is to improve the homogeneity of the final image.
Another purpose of this invention is to improve inking of magnetized dots on the leading edge, while avoiding expending more energy to do this.
Another purpose of the invention is to improve the printing efficiency, namely the ratio between the optical density of an inked magnetic dot and the energy necessary to magnetize the dot concerned.
In this context, this invention proposes a magnetographic printing process consisting of creating magnetized recorded dots on a surface of a magnetic recording element by means of at least one elementary magnetic head, spraying ink particles on each of the magnetized recorded dots in order to form images composed of image dots, magnetized and inked recorded dots being called developed dots, characterized in that it consists of increasing the optical density of developed dots belonging to the leading edge.
This invention also relates to a magnetographic printer comprising at least one elementary magnetic head capable of creating magnetized recorded dots on a surface of the magnetic recording element, means of controlling the elementary magnetic head, means of spraying ink particles onto each of the magnetized recorded dots in order to form images composed of image dots, and characterized in that it comprises means of detection of the leading edge in association with the control means.